Methods for producing and purifying 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compounds, the purified monomers, and polymers derived therefrom

ABSTRACT

Disclosed is a method for producing a purified 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I) 
                         
wherein R 1  is hydrogen or a C 1-25  hydrocarbyl group and R 2  is a hydrogen, a C 1-25  hydrocarbyl group, or a halogen, and wherein the method comprises dissolving a crude phthalimidine compound in an aqueous base solution; precipitating the dissolved, crude phthalimidine compound from the aqueous base solution by adding an acid in an amount effective to lower the pH of the solution to 9.0 to 12.0, to provide a semicrude phthalimidine compound; and isolating the semicrude phthalimidine compound from the aqueous base solution, to provide the purified 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I), and having a phenolphthalein compound content of less than 2,500 ppm, based on the weight of the purified 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine. Subsequent trituration with aqueous methanol and recrystallization from isopropanol can result in product having undetectable levels of phenolphthalein derivatives.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/333,451, filed Dec. 12, 2008, now U.S. Pat. No. 8,247,523 which isincorporated herein by reference in its entirety.

BACKGROUND

The present disclosure generally relates to methods for producing andpurifying 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compounds, thepurified compounds, and polycarbonates as well as other polymers derivedfrom the compounds.

3,3-Bis-(4-hydroxy-phenyl)-3H-isobenzofuran-1-one (hereinafter referredto as phenolphthalein) has been used as an aromatic dihydroxy monomerfor preparing polycarbonates, which are generally characterized withexcellent ductility and high glass transition temperatures. Certainderivatives of phenolphthalein have also been used as aromatic dihydroxymonomers to prepare polycarbonates. For example, polycarbonatehomopolymers have been prepared by an interfacial polycondensationmethod using phosgene and phenolphthalein derivatives such as3,3-bis(4-hydroxyphenyl)phthalimidine and2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (“PPPBP”).

Lin and Pearce (Journal of Polymer Science: Polymer Chemistry Edition,(1981) Vol. 19, pp. 2659-2670) reported the synthesis of PPPBP byrefluxing phenolphthalein and aniline hydrochloride in aniline for 6hours, followed by recrystallization from ethanol. During this reaction,side products are created which, if not removed, can result in the PPPBPhaving an unacceptable purity for use as a monomer or as a comonomer insubsequent polymerization reactions. The impurities in the PPPBPinclude, for example, levels of phenolphthalein or phenolphthaleincompounds that can undesirably produce discoloration in thepolycarbonates and other polymers derived therefrom. Coloration is not adesirable attribute for many commercial applications. U.S. Pat. No.5,344,910 discloses that copolymers of PPPBP were found to have poormelt stability resulting in foamy polymer melts and moldings, anddiscoloration of the polymer during melt processing.

U.S. Publication 2005/0288517 describes a method of purifying2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compounds. The techniquedescribed in U.S. Publication No. 2005/0288517 achievedphenolphthalein-based impurity levels as low as about 300 ppm based onPPPBP weight. While these levels improved the color and stability ofpolymers prepared with the purified PPPBP, further improvements in colorand stability of polymer made with PPPBP are desirable.

It would therefore be desirable to develop a process for furtherimproving the purity of phenolphthalein derivatives such as2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine and PPPBP.

BRIEF SUMMARY

This disclosure relates to a method for producing a purified2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I)

wherein R¹ is hydrogen or a C₁₋₂₅ hydrocarbyl group and R² is hydrogen,a C₁₋₂₅ hydrocarbyl group, or a halogen, and wherein the methodcomprises: heating a reaction mixture comprising a phenolphthaleincompound of formula (II)

wherein R² is hydrogen, a C₁₋₂₅ hydrocarbyl group, or a halogen, aprimary aryl amine of formula (III),

wherein R¹ is hydrogen or a C₁₋₂₅ hydrocarbyl group, and an acidcatalyst, to form a phthalimidine compound of formula (I); precipitatingthe phthalimidine compound from the reaction mixture to provide a crudephthalimidine compound; dissolving the crude phthalimidine compound inan aqueous base solution; precipitating the dissolved, crudephthalimidine compound from the aqueous base solution by adding an acidin an amount effective to lower the pH of the solution to 9.0 to 12.0,to provide a semicrude phthalimidine compound; and isolating thesemicrude phthalimidine compound from the aqueous base solution, toprovide the purified 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine offormula (I), and having a phenolphthalein compound content of less than2,500 ppm, based on the weight of the purified2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine.

In another embodiment, a method for producing a highly purified2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I) comprises:heating a reaction mixture comprising a phenolphthalein compound offormula (II) a primary aryl amine of formula (III and an acid catalyst,to form a phthalimidine compound of formula (I); precipitating thephthalimidine compound from the reaction mixture to provide a crudephthalimidine compound; dissolving the crude phthalimidine compound inan aqueous solution comprising an alkali metal hydroxide, an alkalineearth hydroxide, or a combination comprising at least one of theforegoing metal hydroxides; precipitating the dissolved, crudephthalimidine compound from the aqueous base solution by adding amineral acid in an amount effective to lower the pH of the solution to9.0 to 12.0, to provide a semicrude phthalimidine compound; andisolating the semicrude phthalimidine compound from the aqueous basesolution, washing the isolated phthalimidine compound with dilute acid,then with water, and drying the washed phthalimidine compound to providea purified phthalimidine compound of formula (I); triturating thepurified phthalimidine compound of formula (I) with an aqueous C₁₋₃alcohol to provide a triturated phthalimidine compound; and washing thetriturated phthalimidine compound with aqueous alcohol, then hot waterpreheated to a temperature of 60 to 80° C.; and drying the washedphthalimidine compound to provide the highly purified2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I), having aphenolphthalein compound content of less than 100 ppm, based on theweight of the 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine.

In still another embodiment, a method for producing a purified2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I) comprises:heating a reaction mixture comprising a phenolphthalein compound offormula (II), a primary aryl amine of formula (III), and an acidcatalyst, to form a phthalimidine compound of formula (I); precipitatingthe phthalimidine compound from the reaction mixture to provide a crudephthalimidine compound; dissolving the crude phthalimidine compound inan aqueous base solution; precipitating the dissolved, crudephthalimidine compound from the aqueous base solution by adding an acidin an amount effective to lower the pH of the solution to 1.0 to lessthan 9.0, to provide a semicrude phthalimidine compound; isolating thesemicrude phthalimidine compound from the aqueous base solution, toprovide the 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I);and sequentially triturating the purified phthalimidine of formula (I)at least twice with an aqueous methanol solution to provide a highlypurified 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I),having a phenolphthalein compound content of less than 200 ppm, based onthe weight of the 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine.

This disclosure also relates to purified2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compounds produced by thedisclosed method.

Also disclosed are polycarbonates and other polymers prepared from thepurified 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compounds producedby the disclosed method.

The above described and other features are exemplified by the followingdetailed description.

DETAILED DESCRIPTION

The present disclosure is generally directed to producing and purifyingphenolphthalein derivatives, in particular2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compounds, which are suitablefor use as monomers and/or comonomers for preparing polycarbonates andother polymers. The method generally involves dissolving a crudearyl-3,3-bis(4-hydroxyaryl)phthalimidine compound containing aphenolphthalein contaminant in a basic aqueous solution. A semicrudeproduct is then precipitated from the solution by adding a concentratedacid to achieve a pH from 9.0 to 12.0. The semicrude product is thenfiltered, washed, and dried to provide a semicrude solid product havinga phenolphthalein-based impurity level of less than 2,500 ppm. At leastone aqueous methanol trituration may be performed on the semicrudeproduct to give a purified 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidinecompound. Typically, the amount of residual phenolphthalein-basedimpurity in the purified phthalimidine compound is less than 100 ppm,based on the weight of the purified phthalimidine compound. Subsequenttriturations with aqueous methanol and recrystallization fromisopropanol can produce very highly purified phthalimidine compoundshaving phenolphthalein-based impurities that are not detectable by highpressure liquid chromatography (HPLC) methods.

The 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compounds produced inaccordance with these methods can be used in the manufacture ofpolycarbonates and other polymers having improved properties, such aslower visual coloration and a higher weight average molecular weight.The 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compounds can furtherhave higher degradation temperatures, and/or reduced color upon heating.

The 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compounds produced inaccordance with this disclosure are of formula (I):

wherein R¹ is hydrogen or a C₁₋₂₅ hydrocarbyl group, and R² is hydrogen,a C₁₋₂₅ hydrocarbyl group, or a halogen. In one embodiment, R¹ ishydrogen, a phenyl, or a C₁₋₃ alkyl group, and R² is hydrogen, a C₁₋₃alkyl group, or a halogen.

The 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I) can beprepared by the reaction of a primary aryl amine, e.g., an aniline offormula (III):

wherein R¹ is as defined above; with a phenolphthalein compound offormula (II):

wherein R² is as defined above. An acid catalyst is generally used tofacilitate formation of the phthalimidine compound.

Exemplary acid catalysts include amine salts of mineral acids. Examplesof suitable amines for forming the acid catalysts include primary,secondary, and tertiary amines having any combination of aliphatic andaromatic groups bonded to the amine nitrogen. The mineral acids used forpreparing the amine salts can be present in a fluid phase, for example,in a gaseous phase or in a liquid phase or in a combination of thegaseous and liquid phases. Non-limiting examples of mineral acidsinclude hydrogen chloride liquid, hydrogen chloride gas, sulfuric acid,nitric acid, and the like.

Exemplary amine salt catalysts include primary, secondary, and tertiaryamine hydrochlorides. In one embodiment, the acid catalyst is introducedas a pre-formed salt of an amine and a mineral acid into the reactor. Inanother embodiment, the acid catalyst is generated in the reactor byfirst charging the amine into the reactor, and then adding about ⅓ toabout 1 part by weight of an appropriate mineral acid to phenolphthaleincompound. In another embodiment, the acid catalyst is generated in thereactor by first charging the amine and an appropriate mineral acid intothe reactor, and then adding the phenolphthalein compound. In stillanother embodiment, about 0.1 parts to about 0.3 parts by weight ofhydrogen chloride gas is introduced into a reactor charged with theamine to form an appropriate amount of the amine hydrochloride catalyst.More hydrochloric acid or more hydrogen chloride gas can also used, butis generally not required. A solvent can optionally be used to initiallyform the amine hydrochloride from the primary hydrocarbyl amine. Thesolvent can then be removed (if desired), and the amine catalyst, e.g.,an aryl amine salt, can be added to the reaction mixture.

The reaction of the aryl amine of formula (III) with the phenolphthaleincompound of formula (II) proceeds by a condensation reaction to form thedesired phenolphthalein derivative, e.g., the phthalimidine compound offormula (I). An excess of the aryl amine over the phenolphthaleincompound can be used to keep the reaction proceeding in a forwarddirection. The condensation reaction can occur at a temperature of 130°C. to 180° C., specifically at a temperature of 135° C. to 170° C., morespecifically at a temperature of 135° C. to 160° C. The reaction can beconducted for 5 to 60 hours, more specifically for 40 to 50 hours.

By way of example, the phenolphthalein compound of formula (II) (whereinR² is H and R¹ is phenyl) was reacted with aniline (formula (III)wherein R¹ is H) in the presence of aniline hydrochloride as the acidcatalyst to form 2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine, shownin formula (IV):

In one embodiment, the reaction is conducted at 135° C. to 150° C. overa period from 40 to 50 hours. Water can be removed from the reactionmixture, for example by using an apparatus such as a Dean-Starkapparatus. The so-formed PPPBP can be produced at high yield (70% to90%).

The PPPBP (or other phthalimidine compounds of formula (I)) can beseparated from the reaction mixture by precipitation, for example bypouring the reaction mixture into an antisolvent for the phthalimidinecompound such as water. For example, the reaction mixture can be stirredinto an acidic aqueous solution or into a mixture of ice and a firstconcentrated acid to precipitate a crude phthalimidine compound. Thecrude phthalimidine compound is then isolated, for example by filtrationand washing with water. The first acid is not limited and includeshydrochloric acid, sulfuric acid, sulfurous acid, phosphoric acid, andnitric acid. Typically 3 to 9 molar acid is utilized. The crudephthalimidine compound typically contains the phenolphthalein compoundin an amount of about 0.35 to about 1.00 weight percent (wt. %),although this amount can vary greatly depending on the reactants andreactant conditions.

The crude phthalimidine compound is then dissolved in an aqueous basesolution. The aqueous base can be an alkali metal or alkaline earthmetal hydroxide, carbonate, or bicarbonate. Typically, an aqueous sodiumhydroxide solution is utilized. The aqueous base solution can containfrom 1 to 50% (w/v) of the base. A sufficient amount is used to providean aqueous base solution containing the crude phthalimidine compoundhaving a pH of greater than 12, specifically greater than 14.

Optionally, the aqueous base solution containing the crude phthalimidinecompound is then treated with a solid adsorbent that can removecolor-forming species present in the solution. In one embodiment, acommercially available activated carbon is used. Treatment with theactivated carbon removes color-forming species present in the solution.Exemplary activated carbons include, but are not intended to be limitedto, the NORIT series of activated carbon available from NoritCorporation, and those activated carbons commercially available from E.Merck Company.

In addition to functioning as a decolorizing agent, the activated carbontreatment also aids in selectively adsorbing the2-aryl-3-{(4-hydroxyaryl)(2-hydroxyaryl)}phthalimidine isomericimpurity, as well as any2-aryl-3-{(4-hydroxyaryl)(4-aminoaryl)}phthalimidine isomericimpurities. Thus, one method for purifying a crude2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compound comprises contactingan aqueous base solution of the crude phthalimidine compound with theactivated carbon, removing the activated carbon (e.g., by centrifugationor filtration) to provide treated aqueous base solution containing thecrude phthalimidine compound. This treated aqueous base solution canagain be treated in the same manner, if desired, to provide furtherreductions in the levels of the2-aryl-3-{(4-hydroxyaryl)(2-hydroxyaryl)}phthalimidine impurity and any2-aryl-3-{(4-hydroxyaryl)(4-aminoaryl)}phthalimidine isomericimpurities.

A second concentrated acid is then added to the aqueous base solution(or treated aqueous base solution) containing the crude product. Thesecond concentrated acid can be the same as those above for the firstconcentrated acid. In one embodiment, a mineral acid (specificallyhydrochloric acid) is used. In one embodiment, the acid is added in anamount and over a period of time sufficient to provide a solution pH of1.0 to 12.0. However, it has been found that even higher ultimatepurities can be obtained when the acid is added in an amount and over aperiod of time sufficient to provide a solution pH of 9.0 to 12.0,specifically 9.0 to 11.0, more specifically 9.5 to 10.5. Upon adjustmentof the pH, a semicrude phthalimidine compound precipitates from thesolution. It is also observed that the solution/slurry changes from abright pink to a light pink. It is often advantageous to hold the slurryat the final pH for a period of time, for example, the slurry can bestirred for 1 to 3 hours at room temperature.

The semicrude phthalimidine compound is then isolated from the slurry,for example filtered and washed with dilute acid. The dilute acid can beany of the acids listed above with a concentration from 2 to 6 molar.The semicrude phthalimidine compound can then be washed with water anddried. Drying temperatures can range from 60° C. to 120° C.,specifically 67 to 100° C. Drying can occur under vacuum.

When precipitation is carried out at a relatively lower pH, i.e., of 1.0to less than 9.0, the semicrude phthalimidine compound comprises about0.4000 to 0.7000 wt. % (4,000 to 7,000 ppm) of phenolphthalein compound,specifically about 4,000 to about 6,000 ppm of phenolphthalein compound.The yield of phthalimidine compound is typically about 70% to about 98%,based on the weight of the crude phthalimidine compound.

When precipitation is carried out a pH of 9.0 to 12.0, the semicrudephthalimidine compound has a purity from 98.5 to 99.3 wt. %, andcomprises less than about 0.2500 wt. % (2,500 ppm), specifically about1,000 to about 2,000 ppm of phenolphthalein compound. The yield ofphthalimidine compound is typically about 70% to about 98%, based on theweight of the crude phthalimidine compound.

To obtain a purified phthalimidine compound, at least one trituration isperformed on the semicrude product. Trituration is conducted usingaqueous methanol, in particular a solution comprising 5% to 20% byvolume water and 80 to 95% by volume methanol. In one embodiment,trituration is conducted at an elevated temperature that is below theboiling point of the aqueous methanol, for example 45° C. to 90° C.,more specifically 50° C. to 80° C. Trituration is conducted for a timeeffective to decrease the amount of phenolphthalein compound impurities,for example for 5 minutes to 5 hours, more specifically 30 minutes to 2hours.

The triturated phthalimidine compound is isolated from the aqueousmethanol, for example by filtration. In one embodiment the isolatedphthalimidine compound is washed with hot water (e.g., water preheatedto a temperature of 40° C. to 95°). The washed phthalimidine compoundcan then be dried, optionally under vacuum at a temperature of, e.g.,100° C. to 120° C., to form a purified2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine compound. When the semicrudephthalimidine compound obtained by precipitation at a pH of 1.0 to lessthan 9.0 is used, the purified phthalimidine compound has aphenolphthalein compound content of about 400 to 700 ppm. When thesemicrude phthalimidine compound obtained by precipitation at a pH of9.5 to 12.0 is used, the yield of the purified phthalimidine compound,based on the weight of the phenolphthalein compound is typically from 68to 98%, specifically from 90 to 95%, and the purified phthalimidinecompound has a phenolphthalein compound content of less than 100 ppm,specifically about 20 to about 100 ppm. Purified phthalimidine compoundsobtained by this process (precipitation at a pH of 9.5 to 12.0, followedby a single methanol trituration) can be used directly to producepolymers having low color.

The purified phthalimidine compound can be triturated a second time toprovide a highly purified phthalimidine compound. When the semicrudephthalimidine compound obtained by precipitation at a pH of 1.0 to lessthan 9.5 is used, the highly purified phthalimidine compound has aphenolphthalein compound content of less than 200 ppm, specificallyabout 100 to 200 ppm. When the semicrude phthalimidine compound obtainedby precipitation at a pH of 9.5 to 12.0 is used, the highly purifiedphthalimidine compound has a phenolphthalein content of less than 50ppm, specifically 10 to 50 ppm. The trituration is conducted asdescribed above, using an aqueous methanol solution. Optionally, theproduct isolated from the second trituration is also washed with aqueousmethanol followed by hot water as described above, and dried. The yieldof the highly purified phthalimidine compound can be from 70 to 85 wt.%, based on the weight of the semicrude phthalimidine compound.

If a very highly purified phthalimidine compound is desired, the highlypurified phthalimidine compound can be further recrystallized from asuitable solvent, for example isopropanol. When the semicrudephthalimidine compound obtained by precipitation at a pH of 9.0 to lessthan 12.0 is used, the very highly purified phthalimidine compound has aphenolphthalein compound content that is not detectable by the HPLCmethod described in the experimental section below.

In a specific embodiment of the process described herein, PPPBP (orother phthalimidine compound of formula (I)) is synthesized as describedabove, than separated from the reaction mixture by precipitation, forexample by pouring the reaction mixture into an antisolvent for thephthalimidine compound such as water. For example, the reaction mixturecan be stirred into an acidic aqueous solution or into a mixture of iceand a first concentrated acid to precipitate a crude phthalimidinecompound. The crude phthalimidine compound is then isolated byfiltration and washing with water. The crude phthalimidine compound isthen dissolved in an aqueous solution containing an alkali metalhydroxide, an alkaline earth hydroxide, or a combination comprising atleast one of the foregoing metal hydroxides. Next the dissolved, crudephthalimidine compound is precipitated from the aqueous base solution byadding a mineral acid in an amount effective to lower the pH of thesolution to 9.0 to 12.0, to provide a semicrude phthalimidine compound.The semicrude phthalimidine compound is then isolated from the aqueousbase solution and the isolated phthalimidine compound is washed withdilute acid, then with water, and followed by drying to provide apurified phthalimidine compound of formula (I). The purifiedphthalimidine compound of formula (I) is then triturated with aqueousmethanol to provide a triturated phthalimidine compound. The trituratedphthalimidine compound is washed with aqueous methanol as describedabove, then hot water (preheated to a temperature of 60 to 80° C.) andthe washed phthalimidine compound is dried to provide the highlypurified 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I),having a phenolphthalein compound content of less than 100 ppm, based onthe weight of the 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine. Optionallya second trituration can be performed, optionally followed byrecrystallization from a suitable solvent such as isopropanol asdescribed above.

For convenience, the phenolphthalein (PP) content and typical yields ofPPPBP purified in accordance with the above-described procedures is setforth in the Table below.

Stage Procedure PP (ppm) Yield (%) Crude PPPBP Precipitated fromreaction 5000-7000 — Semicrude After precipitation at pH = 1-2 4000-600098% PPPBP Semicrude After precipitation at pH = 3-4 5000-7000 98% PPPBPSemicrude After precipitation at pH = 9.5 <2500  97%* PPPBP PurifiedPPPBP After precipitation at pH = 1-2, 400-700 85-93% one MeOHtrituration Purified PPPBP After precipitation at pH = 9.5,  <10094-95%* one MeOH trituration Highly purified After precipitation at pH =1-2, 100-200 70-85%  PPPBP two MeOH triturations Highly purified Afterprecipitation at pH = 9.5,  <50 78-85%* PPPBP two MeOH triturations Veryhighly After precipitation at pH = 9.5, N.D. — purified two MeOHtriturations, one PPPBP isopropanol trituration *Based on the weight ofthe semicrude PPPBP N.D.—not detectable

The 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidines, including the exemplary2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (PPPBP), are commerciallyvaluable monomers or comonomers for producing a variety of polymersformed by reactions of the phenolic OH groups of the2-aryl-3,3-bis(4-hydroxyaryl)phthalimidines. Exemplary polymers that canbe produced include homopolymers and copolymers of a polycarbonate, apolyestercarbonate, a polyester, a polyesteramide, a polyimide, apolyetherimide, a polyamideimide, a polyether, a polyethersulfone, apolycarbonate-polyorganosiloxane block copolymer, a copolymer comprisingaromatic ester, ester carbonate, and carbonate repeat units, and apolyetherketone. An example of a copolymer comprising aromatic ester,estercarbonate, and carbonate repeat units is the copolymer produced bythe reaction of a hydroxy-terminated polyester, such as the product ofreaction of isophthaloyl chloride and terephthaloyl chloride withresorcinol, with phosgene and an aromatic dihydroxy compound, such asbisphenol A.

In one embodiment, polycarbonates having low color properties aresynthesized, wherein the polycarbonates include structural units offormula (V):

which are derived from a 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine offormula (I), wherein R¹ and R² are as described previously; and the C═Ostructural units are derived from a C═O donor such as a carbonic aciddiester in a melt transesterification process, or phosgene in aninterfacial process.

Specific polycarbonates are copolycarbonates having structural unitsderived from a phthalimidine compound of formula (I) and a dihydroxycompound of the formula HO—R¹—OH, in particular of formula (VI)HO-A¹-Y¹-A²-OH  (VI)wherein each of A¹ and A² is a monocyclic divalent aromatic group and Y¹is a single bond or a bridging group having one or more atoms thatseparate A¹ from A². In an exemplary embodiment, one atom separates A¹from A². Specifically, each R¹ can be derived from a dihydroxy aromaticcompound of formula (VII):

wherein R^(a) and R^(b) each represent a halogen or C₁₋₁₂ alkyl groupand can be the same or different; and p and q are each independentlyintegers of 0 to 4. X^(a) represents a single bond or a bridging groupconnecting the two hydroxy-substituted aromatic groups, where the singlebond or the bridging group and the hydroxy substituent of each C₆arylene group are disposed ortho, meta, or para (specifically para) toeach other on the C₆ arylene group. In an embodiment, the bridging groupX^(a) is —O—, —S—, —S(O)—, —S(O)₂—, —C(O)—, or a C₁₋₁₈ organic group.The C₁₋₁₈ organic group can be cyclic or acyclic, aromatic ornon-aromatic, and can further comprise heteroatoms such as halogens,oxygen, nitrogen, sulfur, silicon, or phosphorous. The C₁₋₁₈ organicgroup can be disposed such that the C₆ arylene groups connected theretoare each connected to a common alkylidene carbon or to different carbonsof the C₁₋₁₈ organic group. In one embodiment, p and q is each 1, andR^(a) and R^(b) are each a C₁₋₃ alkyl group, specifically methyl,disposed meta to the hydroxy group on each arylene group.

In an embodiment, X^(a) is a substituted or unsubstituted C₃₋₁₈cycloalkylidene, a C₁₋₂₅ alkylidene of formula —C(R^(c))(R^(d))— whereinR^(c) and R^(d) are each independently hydrogen, C₁₋₁₂ alkyl, C₁₋₁₂cycloalkyl, C₇₋₁₂ arylalkyl, C₁₋₁₂ heteroalkyl, or cyclic C₇₋₁₂heteroarylalkyl, or a group of the formula —C(═R^(e))— wherein R^(e) isa divalent C₁₋₁₂ hydrocarbon group. Exemplary groups of this typeinclude methylene, cyclohexylmethylene, ethylidene, neopentylidene, andisopropylidene, as well as 2-[2.2.1]-bicycloheptylidene,cyclohexylidene, cyclopentylidene, cyclododecylidene, andadamantylidene. In another embodiment, X^(a) is a C₁₋₁₈ alkylene group,a C₃₋₁₈ cycloalkylene group, a fused C₆₋₁₈ cycloalkylene group, or agroup of the formula —B¹—W—B²— wherein B¹ and B² are the same ordifferent C₁₋₆ alkylene group and W is a C₃₋₁₂ cycloalkylidene group ora C₆₋₁₆ arylene group.

Other useful aromatic dihydroxy compounds of the formula HO—R¹—OHinclude compounds of formula (VIII):

wherein each R^(h) is independently a halogen atom, a C₁₋₁₀ hydrocarbylsuch as a C₁₋₁₀ alkyl group, a halogen-substituted C₁₋₁₀ alkyl group, aC₆₋₁₀ aryl group, or a halogen-substituted C₆₋₁₀ aryl group, and n is 0to 4. The halogen is usually bromine.

Some illustrative examples of specific aromatic dihydroxy compoundsinclude the following: 4,4′-dihydroxybiphenyl, 1,6-dihydroxynaphthalene,2,6-dihydroxynaphthalene, bis(4-hydroxyphenyl)methane,bis(4-hydroxyphenyl)diphenylmethane,bis(4-hydroxyphenyl)-1-naphthylmethane, 1,2-bis(4-hydroxyphenyl)ethane,1,1-bis(4-hydroxyphenyl)-1-phenylethane,2-(4-hydroxyphenyl)-2-(3-hydroxyphenyl)propane,bis(4-hydroxyphenyl)phenylmethane,2,2-bis(4-hydroxy-3-bromophenyl)propane,1,1-bis(hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane,1,1-bis(4-hydroxyphenyl)isobutene,1,1-bis(4-hydroxyphenyl)cyclododecane,trans-2,3-bis(4-hydroxyphenyl)-2-butene,2,2-bis(4-hydroxyphenyl)adamantane,alpha,alpha′-bis(4-hydroxyphenyl)toluene,bis(4-hydroxyphenyl)acetonitrile,2,2-bis(3-methyl-4-hydroxyphenyl)propane,2,2-bis(3-ethyl-4-hydroxyphenyl)propane,2,2-bis(3-n-propyl-4-hydroxyphenyl)propane,2,2-bis(3-isopropyl-4-hydroxyphenyl)propane,2,2-bis(3-sec-butyl-4-hydroxyphenyl)propane,2,2-bis(3-t-butyl-4-hydroxyphenyl)propane,2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane,2,2-bis(3-allyl-4-hydroxyphenyl)propane,2,2-bis(3-methoxy-4-hydroxyphenyl)propane,2,2-bis(4-hydroxyphenyl)hexafluoropropane,1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethylene,1,1-dibromo-2,2-bis(4-hydroxyphenyl)ethylene,1,1-dichloro-2,2-bis(5-phenoxy-4-hydroxyphenyl)ethylene,4,4′-dihydroxybenzophenone, 3,3-bis(4-hydroxyphenyl)-2-butanone,1,6-bis(4-hydroxyphenyl)-1,6-hexanedione, ethylene glycolbis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)ether,bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)sulfoxide,bis(4-hydroxyphenyl)sulfone, 9,9-bis(4-hydroxyphenyl)fluorine,2,7-dihydroxypyrene,6,6′-dihydroxy-3,3,3′,3′-tetramethylspiro(bis)indane (“spirobiindanebisphenol”), 3,3-bis(4-hydroxyphenyl)phthalimide,2,6-dihydroxydibenzo-p-dioxin, 2,6-dihydroxythianthrene,2,7-dihydroxyphenoxathin, 2,7-dihydroxy-9,10-dimethylphenazine,3,6-dihydroxydibenzofuran, 3,6-dihydroxydibenzothiophene, and2,7-dihydroxycarbazole, resorcinol, substituted resorcinol compoundssuch as 5-methyl resorcinol, 5-ethyl resorcinol, 5-propyl resorcinol,5-butyl resorcinol, 5-t-butyl resorcinol, 5-phenyl resorcinol, 5-cumylresorcinol, 2,4,5,6-tetrafluoro resorcinol, 2,4,5,6-tetrabromoresorcinol, or the like; catechol; hydroquinone; substitutedhydroquinones such as 2-methyl hydroquinone, 2-ethyl hydroquinone,2-propyl hydroquinone, 2-butyl hydroquinone, 2-t-butyl hydroquinone,2-phenyl hydroquinone, 2-cumyl hydroquinone, 2,3,5,6-tetramethylhydroquinone, 2,3,5,6-tetra-t-butyl hydroquinone, 2,3,5,6-tetrafluorohydroquinone, 2,3,5,6-tetrabromo hydroquinone, or the like, orcombinations comprising at least one of the foregoing dihydroxycompounds.

Specific examples of bisphenol compounds of formula (VII) include1,1-bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane,2,2-bis(4-hydroxyphenyl)propane (hereinafter “bisphenol A” or “BPA”),2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane,1,1-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)n-butane,2,2-bis(4-hydroxy-2-methylphenyl)propane,1,1-bis(4-hydroxy-t-butylphenyl)propane,3,3-bis(4-hydroxyphenyl)phthalimidine, and1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (DMBPC). Combinationscomprising at least one of the foregoing dihydroxy compounds can also beused. In one specific embodiment, the polycarbonate is a linearhomopolymer derived from bisphenol A, in which each of A¹ and A² isp-phenylene and Y¹ is isopropylidene in formula (3).

Exemplary carbonic acid diesters useful in the formation of thepolycarbonates in a melt transesterification process are of formula(IX):(ZO)₂C═O  (IX)wherein each Z is independently an unsubstituted or substituted C₁₋₁₂alkyl radical, or an unsubstituted or substituted C₆₋₂₂ aryl radical.Examples of carbonic acid diesters include, but are not limited to,ditolyl carbonate, m-cresyl carbonate, dinaphthyl carbonate, diphenylcarbonate, diethyl carbonate, dimethyl carbonate, dibutyl carbonate,dicyclohexyl carbonate, and combinations thereof. Diphenyl carbonate iswidely used as a carbonic acid diester due to its low cost and readyavailability on a commercial scale. Use of activated aromatic carbonatesthat are more reactive than diphenyl carbonate is also contemplated.Specific non-limiting examples of activated aromatic carbonates includebis(o-methoxycarbonylphenyl)carbonate, bis(o-chlorophenyl)carbonate,bis(o-nitrophenyl)carbonate, bis(o-acetylphenyl)carbonate,bis(o-phenylketonephenyl)carbonate, bis(o-formylphenyl)carbonate.Unsymmetrical combinations of these structures are also contemplated.Exemplary ester-substituted diaryl carbonates include, but are notlimited to, bis(methylsalicyl)carbonate (CAS Registry No. 82091-12-1)(also known as BMSC or bis(o-methoxycarbonylphenyl)carbonate), bis(ethylsalicyl)carbonate, bis(propyl salicyl)carbonate,bis(butylsalicyl)carbonate, bis(benzyl salicyl)carbonate, bis(methyl4-chlorosalicyl)carbonate, and the like. In one embodiment, BMSC is usedin the melt transesterification process.

The melt transesterification process is generally carried out bycombining a catalyst, the carbonic acid diester of formula (IX), thephthalimidine compound of formula (I), and optionally a dihydroxycomonomer; and mixing the reaction mixture under reactive conditions fora time period effective to produce the polycarbonate product. Exemplarymelt transesterification catalysts include alkali metal compounds,alkaline earth metal compounds, tetraorganoammonium compounds,tetraorganophosphonium compounds, and combinations comprising at leastone of the foregoing catalysts. Specific examples of alkali metalcompounds or alkaline earth metal compounds include, but are not limitedto, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesiumhydroxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate,potassium carbonate, lithium carbonate, sodium acetate, potassiumacetate, sodium stearate, potassium stearate, sodium hydroxyborate,sodium phenoxyborate, sodium benzoate, potassium benzoate, lithiumbenzoate, disodium hydrogen phosphate, dipotassium hydrogen phosphate,dilithium hydrogen phosphate, disodium salts, dipotassium salts, anddilithium salts of bisphenol A, and sodium salts, potassium salts,lithium salts of phenol, and the like. Specific examples oftetraorganoammonium compounds and tetraorganophosphonium compoundsinclude, but are not limited to tetramethylammonium hydroxide,tetrabutylammonium hydroxide, tetraethylphosphonium hydroxide,tetrabutylphosphonium acetate, tetrabutylphosphonium hydroxide, and thelike.

In one embodiment, the catalyst is tetrabutylphosphonium acetate. In analternative embodiment, the catalyst comprises a mixture of an alkalimetal salt or alkaline earth metal salt with at least one quaternaryammonium compound, at least one quaternary phosphonium compound, or amixture thereof. For example, the catalyst can be a mixture of sodiumhydroxide and tetrabutylphosphonium acetate. In another embodiment, thecatalyst is a mixture of sodium hydroxide and tetramethylammoniumhydroxide. In yet another embodiment, the catalyst comprises the salt ofa non-volatile inorganic acid, for example alkali metal salts ofphosphites; alkaline earth metal salts of phosphites; alkali metal saltsof phosphates; and alkaline earth metal salts of phosphates, includingbut not limited to NaH₂PO₃, NaH₂PO₄, Na₂H₂PO₃, KH₂PO₄, CsH₂PO₄,Cs₂H₂PO₄, or a mixture thereof. In one embodiment, thetransesterification catalyst comprises both the salt of a non-volatileacid and a basic co-catalyst such as an alkali metal hydroxide. Thisconcept is exemplified by the use of a combination of NaH₂PO₄ and sodiumhydroxide as the transesterification catalyst.

Any of the catalysts disclosed above can be used as combinations of twoor more substances. Moreover, the catalyst can be added in a variety offorms. For example, the catalyst can be added as a solid as a powder, orit can be dissolved in a solvent, for example, in water or alcohol. Thetotal catalyst composition can be about 1×10⁻⁷ to about 2×10⁻³ moles,and in other embodiments, about 1×10⁻⁶ to about 4×10⁻⁴ moles, for eachmole of the combination of, for example, the purified PPPBP and thearomatic dihydroxy comonomer.

The progress of the polymerization reaction can be monitored bymeasuring the melt viscosity or the weight average molecular weight ofthe reaction mixture using techniques known in the art such as gelpermeation chromatography. These properties can be measured by takingdiscreet samples or can be measured on-line. After the desired meltviscosity and/or molecular weight is reached, the final polycarbonateproduct can be isolated from the reactor in a solid or molten form. Themethod of making polycarbonates as described in the preceding sectionscan be made in a batch or a continuous process.

In one embodiment, the melt-polymerized polycarbonate is prepared in anextruder in the presence of one or more catalysts. The reactants for thepolymerization reaction can be fed to the extruder in powder or moltenform. In one embodiment, the reactants are dry blended prior to additionto the extruder. The extruder can be equipped with pressure reducingdevices (e.g., vents) that serve to remove the activated phenolbyproduct and thus drive the polymerization reaction toward completion.The molecular weight of the polycarbonate product can be manipulated bycontrolling, among other factors, the feed rate of the reactants, thetype of extruder, the extruder screw design and configuration, theresidence time in the extruder, the reaction temperature, and thepressure reducing techniques present on the extruder. The molecularweight of the polycarbonate product can also depend upon the structuresof the reactants and the catalyst employed. Many different screw designsand extruder configurations are commercially available that use singlescrews, double screws, vents, back flight and forward flight zones,seals, side-streams, and sizes.

Alternatively, the polycarbonates can be prepared by an interfacialpolymerization process. Although the reaction conditions for interfacialpolymerization can vary, an exemplary process generally involvesdissolving or dispersing a dihydric phenol reactant in aqueous causticsoda or potash, adding the resulting mixture to a water-immisciblesolvent medium, and contacting the reactants with a carbonate precursorin the presence of a catalyst such as triethylamine and/or a phasetransfer catalyst, under controlled pH conditions, e.g., about 8 toabout 12. The most commonly used water immiscible solvents includemethylene chloride, 1,2-dichloroethane, chlorobenzene, toluene, and thelike.

Exemplary carbonate precursors for interfacial polymerization include acarbonyl halide such as carbonyl bromide or carbonyl chloride, or ahaloformate such as a bishaloformates of a dihydric phenol (e.g., thebischloroformates of bisphenol A, hydroquinone, or the like) or a glycol(e.g., the bishaloformate of ethylene glycol, neopentyl glycol,polyethylene glycol, or the like). Combinations comprising at least oneof the foregoing types of carbonate precursors can also be used. In anexemplary embodiment, an interfacial polymerization reaction to formcarbonate linkages uses phosgene as a carbonate precursor, and isreferred to as a phosgenation reaction.

Among the phase transfer catalysts that can be used for interfacialpolymerization are tetraorganoammonium compounds andtetraorganophosphonium compounds of the formula (R³)₄Q⁺X, wherein eachR³ is the same or different, and is a C₁₋₁₀ alkyl group; Q is a nitrogenor phosphorus atom; and X is a halogen atom or a C₁₋₈ alkoxy group orC₆₋₁₈ aryloxy group. Exemplary phase transfer catalysts include, forexample, [CH₃(CH₂)₃]₄NX, [CH₃(CH₂)₃]₄PX, [CH₃(CH₂)₅]₄NX, [CH₃(CH₂)₆]₄NX,[CH₃(CH₂)₄]₄NX, CH₃[CH₃(CH₂)₃]₃NX, and CH₃[CH₃(CH₂)₂]₃NX, wherein X isCl⁻, Br⁻, a C₁₋₈ alkoxy group or a C₆₋₁₈ aryloxy group. An effectiveamount of a phase transfer catalyst can be about 0.1 to about 10 wt %based on the weight of bisphenol in the phosgenation mixture. In anotherembodiment an effective amount of phase transfer catalyst can be about0.5 to about 2 wt % based on the weight of bisphenol in the phosgenationmixture.

All types of polycarbonate end groups are contemplated as being usefulin the polycarbonate composition, provided that such end groups do notsignificantly adversely affect desired properties of the compositions.Branched polycarbonate blocks can be prepared by adding a branchingagent during polymerization. A chain stopper (also referred to as acapping agent) can be included during polymerization. The chain stopperlimits molecular weight growth rate, and so controls molecular weight inthe polycarbonate. Exemplary chain stoppers include certainmono-phenolic compounds, mono-carboxylic acid chlorides, and/ormono-chloroformates.

The interfacial method described above can be suitably adapted toproduce polycarbonates through the intermediate formation of2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine bischloroformate. This methodis sometimes called the bischloroformate polymerization method. In oneembodiment, the method comprises reacting a2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine with phosgene in an organicsolvent, and then reacting the bischloroformate either with a2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine, or an aromatic dihydroxycompound in the presence of an acid acceptor and an aqueous base to formthe polycarbonate. The interfacial polymerization method and thebischloroformate polymerization method can be carried in a batch or acontinuous mode using one or more reactor systems. To carry out theprocess in a continuous mode, one or more continuous reactors, such asfor example, a tubular reactor can be used. In one embodiment, thecontinuous method comprises introducing into a tubular reactor systemphosgene, at least one solvent (example, methylene chloride), at leastone bisphenol, aqueous base, and optionally one or more catalysts(example, a trialkylamine) to form a flowing reaction mixture. Theflowing mixture is then passed through the tubular reactor system untilsubstantially all of the phosgene has been consumed. The resultingmixture is next treated with a mixture comprising an aqueous base, atleast one endcapping agent, optionally one or more solvents, and atleast one catalyst. The endcapped polycarbonate thus formed iscontinuously removed from the tubular reactor system.

The processes disclosed herein can advantageously be used to prepare,for example, PPPBP homopolycarbonate and copolycarbonates having aweight average molecular weight (Mw) of about 3,000 to about 150,000Daltons and a glass transition temperature (Tg) of about 80° C. to about300° C. The number average molecular weights (Mn) of thehomopolycarbonate and copolycarbonates can be from about 1,500 to about75,000 Daltons.

Polymers comprising structural units derived from the phthalimidinecompounds, in particular PPPBP can be used to manufacture polymer blendscomprising the polymer and at least one other thermoplastic polymer. Theat least one other thermoplastic polymer includes vinyl polymers,acrylic polymers, polyacrylonitrile, polystyrenes, polyolefins,polyesters, polyurethanes, polyamides, polysulfones, polyimides,polyetherimides, polyphenylene ethers, polyphenylene sulfides, polyetherketones, polyether ether ketones, ABS resins, polyethersulfones,poly(alkenylaromatic) polymers, polybutadiene, polyacetals,polycarbonates, polyphenylene ethers, ethylene-vinyl acetate copolymers,polyvinyl acetate, liquid crystal polymers, ethylene-tetrafluoroethylenecopolymer, aromatic polyesters, polyvinyl fluoride, polyvinylidenefluoride, polyvinylidene chloride, tetrafluoroethylene,polycarbonate-polyorganosiloxane block copolymers, copolymers comprisingaromatic ester, estercarbonate, and carbonate repeat units, andcombinations comprising at least one of the foregoing polymers.

The polymers and polymer blends described hereinabove are valuable forproducing articles. In one embodiment, an article comprises a polymercomprising structural units derived from a2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I) prepared byfollowing the process described above.

Polymers, particularly polycarbonate homopolymers and copolymerscomprising structural units derived from the high purity2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine in general, and PPPBP inparticular exhibit lower visual coloration. As such, these polycarbonatepolymers are useful for producing articles having a number of usefulproperties, including lower visual color, among others. Thepolycarbonate homopolymers and copolymers have high glass transitiontemperatures of higher than or equal to about 180° C. One of the uniqueproperties of these polycarbonates, especially those that have glasstransition temperatures of greater than or equal to about 180° C. isthat during melt processing they exhibit a shear-thinning behavior. Thatis, the polymers have the ability to flow under an applied shear.Therefore, standard melt processing equipment used for BPApolycarbonates can advantageously be used for producing articles. Thepolycarbonates also have high transparency, as measured by percent lighttransmission, of greater than or equal to about 85 percent.

In addition to the polymer, the thermoplastic compositions comprisingthe polymers can include various additives ordinarily incorporated intopolymer compositions of this type, with the proviso that the additive(s)are selected so as to not significantly adversely affect the desiredproperties of the thermoplastic composition, in particular low color.Such additives can be mixed at a suitable time during the mixing of thecomponents for forming the composition. Exemplary additives includefillers, reinforcing agents, antioxidants, heat stabilizers, lightstabilizers, ultraviolet (UV) light stabilizers, plasticizers,lubricants, mold release agents, antistatic agents, colorants such assuch as titanium dioxide, carbon black, and organic dyes, surface effectadditives, radiation stabilizers, flame retardants, and anti-dripagents. A combination of additives can be used, for example acombination of a heat stabilizer, mold release agent, and ultravioletlight stabilizer. In general, the additives are used in the amountsgenerally known to be effective. The total amount of additives (otherthan any impact modifier, filler, or reinforcing agents) is generally0.01 to 5 wt. %, based on the total weight of the composition.

The methods described herein are further illustrated by the followingnon-limiting examples.

EXAMPLES

In the following examples, molecular weights were measured by gelpermeation chromatography using polystyrene standards.

Glass transition temperatures of the polycarbonates were measured bydifferential scanning calorimetry by heating the sample at the rate of10° C. to 20° C. per minute under nitrogen.

Purity of 2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (PPPBP) andphenolphthalein (PP) content were determined by HPLC. HPLC analysis wasperformed using a solution of about 50 milligrams of the sampledissolved in about 10 milliliters (mL) of methanol. The HPLC instrumentwas equipped with a C18 (reverse phase) column maintained at atemperature of 40° C., and an ultraviolet detector capable of detectingcomponents at a wavelength of 230 nanometers. A solvent mixture ofmethanol and water of varying relative proportions was used. The flowrate was maintained at 1 milliliter per minute. Area percent assay wascomputed from the area value for each peak detected in the chromatogramdivided by the total area from all peaks detected. To determine weightpercent, calibration curves for PPPBP and PP were first generated. Thenthe weight percent of a given component in a sample was calculated usingthese calibration curves. The PP detection limit for the method is 10ppm.

Heat aging stability of polymers was determined by measuring the numberaverage molecular weight (Mn) and weight average molecular weight (Mw)of the polymers by gel permeation chromatography as described above,initially and after 7 days of aging at 160° C. and 180° C.

YI was determined using a Macbeth Instrument. The APHA of the polymersample was measured on a 2.5 weight percent (weight/volume) solution indichloromethane using a Macbeth Instrument. The APHA shift relative toblank (dichloromethane) is given as the APHA for the polymer sample.

Examples A-F

In these examples, a crude PPPBP was purified by precipitation at arange of pH values. To obtain the crude PPPBP, a mixture of PP (100 g,0.31 moles), aniline (117 g, 1.25 moles), and concentrated aqueoushydrochloric acid (33 ml, 0.34 moles) was heated under reflux at atemperature of about 140° C. to about 145° C. for 45 hours undernitrogen. The resulting dark solution was then stirred into a mixture ofwater and concentrated HCl. The violet colored, crystalline crude PPPBPproduct was separated by filtration and washed with water.

Samples of the crude crystals (121 g) were then dissolved in 275 mL of5% (w/v) sodium hydroxide solution. The solution was treated twice with12 g of activated carbon, and then filtered. The filtrate was treated bydrop-wise addition of concentrated HCl with stirring, until the filtrateachieved the pH indicated in Table 1. The slurry containing PPPBP solidswas stirred for one hour after the desired pH was attained. Wherepossible, the solid phthalimidine compound was then filtered, washedwith 5 M HCl, and then washed with water until the water washings wereneutral, and dried under vacuum at 110° C. to yield semicrude PPPBP. ThepH of the filtrate at which the precipitation was carried out, the wt. %of PP in the semicrude PPPBP, and the percent recovery (based on theweight of the crude PPPBP) is shown in the Table 1.

TABLE 1 Example Treatment of Crude PPPBP % of PP % Recovery Crude —0.4516 NA A* pH = 12.5 No solid formed NA B pH = 11.5 0.1122 68 C pH =10.5 0.0693 86 D pH = 10.0 0.2300 97 E pH = 9.5 0.2069 97 F pH = 1.70.4304 98 *Comparative NA—Not applicableAs can be seen from the data in the Table 1, precipitation of semicrudePPPBP at a filtrate pH from 1.7 to 10.5 provides good recovery.Unexpectedly, precipitation of semicrude PPPBP at a filtrate pH from 9.5to 10.5 results in both excellent recovery and significant removal of PPimpurities from the PPPBP.

Example 1 Preparation of Semicrude PPPBP by Precipitation at pH=9.5

A mixture of PP (50 g), aniline (58.5 g), and concentrated aqueoushydrochloric acid (10 M, 16.4 g) was heated under reflux at atemperature of about 140° C. to about 145° C. for 45 hours undernitrogen, with removal of water using a Dean-Stark apparatus. Theresulting dark solution was then stirred into a mixture of ice andconcentrated HCl. The violet colored, crystalline crude PPPBP productwas separated by filtration and washed with water. At this stage, thecrude PPPBP typically has a PP content of 0.5 to 0.7% by weight of thecrude PPPBP. In this example, the crude PPPBP had a purity of 99.3139%as determined by HPLC, and a PP content of 0.5378 wt. % (5,378 ppm).

The crude crystals (20 g) were then dissolved in 130 mL of 4% (w/v)sodium hydroxide solution. The solution was treated twice with 2 g eachof activated carbon, and then filtered. The filtrate was treated bydrop-wise addition of concentrated HCl with stirring. The aqueous basesolution changed from a bright pink solution to a pale pink, thickslurry with a pH of 9.5. The slurry was stirred for one hour after thedesired pH was attained. The precipitated phthalimidine compound wasthen filtered, washed with dilute HCl (5 M), and then washed with wateruntil the water washings were neutral, and dried under vacuum at 70° C.The semicrude PPPBP crystalline solid was obtained in a yield of 97.9%based on the crude PPPBP crystals, and had a purity of 99.65%, with a PPcontent of 0.2095 wt. % (2,095 ppm).

Example 2 Preparation of Purified PPPBP (Single Trituration)

A portion of the semicrude PPPBP product (15 g) of Example 1 wastriturated at reflux temperature (70° C.) once for one hour usingaqueous methanol (75 mL, 90% MeOH v/v). Trituration was followed bycooling to room temperature, then filtration of the solid PPPBP, whichwas then washed with 15 mL of aqueous methanol and then 1 mL of hotwater (75° C.). The hot water-treated product was dried under vacuum at110° C. to provide purified PPPBP (14.12 g) having a purity of 99.91% asdetermined by HPLC and a PP content of 0.0085 wt. % (85 ppm). The yieldof the purified product was 94.1%, based on the semicrude PPPBP.

Example 3 Preparation of Highly Purified PPPBP (Double Trituration)

A portion of the semicrude PPPBP (20 g), prepared as described inExample 1 (except that precipitation was carried out at a pH of 1-2),was subjected to two sequential triturations with aqueous methanol. Thesemicrude PPPBP had a PP content of 0.45149% by weight, based on thesemicrude PPPBP. A first trituration with 100 mL of aqueous methanol(90% MeOH v/v) at reflux temperature (70° C.) was followed by cooling toroom temperature, filtration of the solid PPPBP, washing with 20 mL ofaqueous methanol and suction drying. The suction-dried PPPBP after thefirst methanol trituration was obtained in a yield of 90.5%, based onthe semicrude PPPBP, and had a PP content of 0.05296 wt. %, based on theweight of the suction-dried PPPBP.

This PPPBP was then subjected to a second trituration with aqueousmethanol (100 mL, 90% MeOH v/v) at reflux temperature (70° C.).Trituration was followed by cooling to room temperature, then filtrationof solid PPPBP, washing with 15 mL of aqueous methanol and 20 mL of hotwater (75° C.). The hot water-treated product was dried under vacuum at110° C. to provide a highly purified PPPBP having a PP content of0.00127 wt. % (12.7 ppm), based on the weight of the residue. The yieldwas 91%, based on the suction-dried PPPBP used for the secondtrituration. The overall recovery of the highly purified PPPBP was 82%,based on the weight of the semicrude PPPBP.

Example 4 Preparation of Very Highly Purified PPPBP (Double Triturationand Crystallization)

Another portion of the semicrude PPPBP (60 g), prepared as described inExample 1, was subjected to two sequential triturations with aqueousmethanol (240 mL each), followed by crystallization with aqueousisopropanol (250 mL, 90% isopropanol v/v). After each aqueous methanoltrituration, the solid PPPBP was filtered and washed with 60 mL ofaqueous methanol and dried by suction. Crystallization with isopropanolwas followed by hot water treatment. The hot water-treated product wasdried under vacuum at 110° C. to provide a very highly purified PPPBPwherein the PP was not detectable using HPLC as described above. Inaddition, the product did not give any pink coloration with sodiumhydroxide solution. The yield was 74%, based on the weight of thesemicrude PPPBP used for the triturations, and the purity of the veryhighly purified PPPBP was 99.95 wt % by HPLC.

Example 5 (Comparative)

This example is in accordance with the commercial process for preparingPPPBP as described in U.S. Patent Publication No. 2005/0288517.Accordingly, a mixture of PP (20 g), aniline hydrochloride (20 g), and60 mL of aniline was heated under reflux at a temperature of about 180to about 185° C. for 5 hours under nitrogen. The resulting dark solutionwas then stirred into a mixture of 100 grams of ice and 70 grams ofconcentrated HCl. The crystalline, violet-colored product was filteredoff and washed with water. The crystals were then dissolved in anice-cold 10% (w/v) sodium hydroxide solution. The solution was treatedwith 0.2 g active carbon, and then filtered. Upon drop-wise addition ofconcentrated HCl into the stirred filtrate, the color changed to brightpink, then to a pure white, thick slurry having a pH of 3 to 4. Theprecipitated PPPBP was then washed to neutral with water and dried undervacuum at 70° C. The semicrude PPPBP crystals had a melting point of 288to 291° C. The yield was 79%, based on the weight of the starting PP. Atthis stage, the crystals have a PP content of 5000 to 7000 ppm.

Double crystallization from ethanol, followed by drying the crystalsunder vacuum at 150° C. yielded a PPPBP product having a PP content of274 pm. In contrast, a single trituration with aqueous methanol yieldsPPPBP having a PP content of less than 500 ppm.

Alternatively, the semicrude PPPBP crystals (20 g) are triturated withaqueous methanol (72 mL methanol and 8 mL water) at reflux for one hour,cooled to room temperature, filtered, washed with 20 mL of aqueousmethanol, washed with 20 mL of hot water (75° C.), and dried undervacuum for 14 hours at 110° C., to provide a PPPBP product having a PPcontent of 300 to 350 ppm.

Examples 1A, 1B, 2A, and 3A

The precipitation procedure of Example 1 and the trituration proceduresof Examples 2 and 3 were repeated using a semicrude PPPBP containing0.4516 wt. % of PP. In Example 1A, the precipitation procedure ofExample 1 was followed, except that the pH of the solution was adjustedto about 1 to 2. In Example 1B, the precipitation procedure of Example 1was followed, with the pH of the solution being adjusted to 9.5. InExample 2A, the product of Example 1A (precipitation at pH of about 1 to2) was purified using the single trituration procedure of Example 2. InExample 3A, the product of Example 1A (precipitation at pH of about 1 to2) was purified using the double trituration procedure of Example 3.

The wt. % of PP and the yield for each Example is shown in Table 2. Thepercent yield is based on the weight of semicrude PPPBP.

TABLE 2 Ex. Procedure % PP % Yield — Semicrude PPPBP 0.4516 1A* Afterprecipitation at pH = about 1-2 0.4304 98% 1B After precipitation at pH= 9.5 0.2069 97% 2A After precipitation at pH = about 1-2, and 0.0529690.5%   one MeOH trituration 3A After precipitation at pH = about 1-2,and 0.00127 82% two MeOH triturations *Control

As can be seen from the results shown in Table 2, aqueous methanoltrituration can be used to remove PP from semicrude PPPBP containinghigh amounts of PP. Two sequential methanol triturations are highlyeffective in producing purified PPPBP having a PP content below about200 ppm.

Examples 1C, 1D, 2B, and 3B

The precipitation procedure of Example 1 and the trituration proceduresof Examples 2 and 3 were repeated using a semicrude PPPBP containing0.5378 wt. % of PP. In Example 1C, the precipitation procedure ofExample 1 was followed, except that the pH of the solution was adjustedto about 3 to 4. In Example 1D, the precipitation procedure of Example 1was followed, with the pH of the solution being adjusted to 9.5. InExample 2B, the product of Example 1D (precipitation at pH of 9.5) waspurified using the single trituration procedure of Example 2. In Example3B, the product of Example 1D (precipitation at pH of 9.5) was purifiedusing the double trituration procedure of Example 3.

The wt. % of PP, percent purity of the PPPBP, and the yield for eachExample is shown in Table 3. The percent yield is based on the weight ofsemicrude PPPBP.

TABLE 3 % Purity % Ex. Stage fo PPPBP % PP Yield — Semicrude PPPBP0.5378 1C* After precipitation at pH = 3-4 0.5310   98% 1D Afterprecipitation at pH = 9.5 99.785 0.0786   97% 2B After precipitation atpH = 9.5 and 99.926 0.0099 93.8% one MeOH trituration 3B Afterprecipitation at pH = 9.5 and 99.955 0.0011 91.9% two MeOH triturations*Control

As can be seen from the results shown in Table 3, aqueous methanoltrituration can be used to remove PP from semicrude PPPBP containinghigh amounts of PP. Two sequential methanol triturations are highlyeffective to produce purified PPPBB having a PP content below about 50ppm.

Example 6

The purified PPPBP of Example 4 and Example 5 were used to preparecopolymers of PPPBP and bisphenol A using an interfacial process.

The reaction setup consisted of 4-necked, round bottom flask fitted withtwo dropping funnels and a mechanical stirrer. The flask was chargedwith BPA and PPPBP monomers in the amounts shown in Table 4, water (100mL), dichloromethane (100 mL), and the phase transfer catalyst. Thecontents were stirred under nitrogen blanket. To this stirred slurry, asolution of triphosgene in dichloromethane and an aqueous sodiumhydroxide solution were added dropwise through separate droppingfunnels. A sufficient amount of sodium hydroxide was added to maintainpH at 5 to 6. After stirring for another 30 minutes, the pH was raisedto 10 to 11 by the addition of aqueous sodium hydroxide, to consumeexcess triphosgene. To this slurry, triethylamine and p-cumyl phenolwere added and pH was again raised to about 12 by the addition ofaqueous sodium hydroxide. Stirring was continued for another 10 minutes.Completion of reaction was inferred by increase of viscosity of theslurry. The dichloromethane layer was then thoroughly washed with diluteHCl, followed by washing with water. The polymer was obtained by theaddition of sufficient methanol to the dichloromethane solution withstirring, filtration of the solid, and drying at 110° C.

TABLE 4 Molar Component Mol. Wt. Wt. added Amount ratio PPPBP 391 11.73g 0.03 moles 3 BPA 228.28 15.97 g 0.07 moles 7 Triphosgene 16.75 g NaOH40   15 g 30% solution (w/v) Triethylamine   200 μL p-cumyl phenol   450mg HCl  1% soln

Short- and long-term heat aging stability of the two polymers was thendetermined. The color stability and heat aging results are summarized inTables 5 and 6.

TABLE 5 PP content Short-term Heat Aging Stability of the (340° C., 5minutes) Source of polymer Initial After Heating PPPBP (ppm)¹ YI Mn MwYI Mn Mw Ex. 4 N.D. 4 12987 32100 13 8925 19020 Ex. 5 82 5 10823 2942269 5158 10823 ¹Calculated based on the PP content of the PPPBP monomer

The data in Table 5 demonstrate an unexpected improvement in theshort-term heat aging properties of copolymers produced using thepurified PPPBP of Example 4. In particular, the color change in heataged samples (340° C., 5 minutes) is significantly lower. Further, thepercent decrease in the Mn and Mw (31% and 41%, respectively) ofcopolymers made using the PPPBP of Example 4 is significantly smallerthan the decrease in Mn and Mw (52% and 63%, respectively) of copolymersmade using the PPPBP of the prior art (Example 5).

TABLE 6 Long-term Heat Aging Stability (7 days) Source of Initial 160°C. 180° C. PPPBP PP (ppm)¹ Mn Mw Mn Mw Mn Mw Ex. 4 N.D. 11201 28855 737314527 1333 9096 Ex. 5 82 6640 13471 544 1274 194 266 ¹Calculated basedon the PP content of the PPPBP monomer

The data in Table 6 demonstrates an unexpected degree of improvement inthe properties of copolymers produced using the purified PPPBP ofExample 4. In particular, after heat aging at 160° C. and 180° C., thepercent decrease in Mn (34% and 88%, respectively) of copolymers madeusing the PPPBP of Example 4 is significantly smaller than the decreasein the Mw (92% and 97%, respectively) of copolymers made using the PPPBPof the prior art (Example 5). Similarly, after heat aging at 160° C. and180° C., the percent decrease in Mw (50% and 68%, respectively) ofcopolymers made using the PPPBP of Example 4 is significantly smallerthan the decrease in the Mw (91% and 98%, respectively) of copolymersmade using the PPPBP of the prior art (Example 5).

For the purposes of this disclosure, the term “hydrocarbyl” is definedherein as a monovalent moiety formed by removing a hydrogen atom from ahydrocarbon. Representative hydrocarbyls are alkyl groups having 1 to 25carbon atoms, such as, for example, methyl, ethyl, propyl, butyl,pentyl, hexyl, heptyl, octyl, nonyl, undecyl, decyl, dodecyl, octadecyl,nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, and the isomericforms thereof; aryl groups having 6 to 25 carbon atoms, such asring-substituted and ring-unsubstituted forms of phenyl, tolyl, xylyl,naphthyl, biphenyl, tetraphenyl, and the like; arylalkyl groups having 7to 25 carbon atoms, such as ring-substituted and ring-unsubstitutedforms of benzyl, phenethyl, phenpropyl, phenbutyl, naphthoctyl, and thelike; and cycloalkyl groups, such as cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and the like. The term“aryl’ as used herein refers to various forms of aryl groups that havebeen described hereinabove for the “hydrocarbyl” group.

The terms “comprising” (and its grammatical variations) as used hereinis used in the inclusive sense of “having” or “including” and not in theexclusive sense of “consisting only of”. The terms “a” and “the” as usedherein are understood to encompass the plural as well as the singular.

All publications, patents and patent applications cited in thisspecification are herein incorporated by reference, and for any and allpurposes, as if each individual publication, patent or patentapplication were specifically and individually indicated to beincorporated by reference. In the case of inconsistencies, the presentdisclosure will prevail.

While the disclosure has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes can be made and equivalents can be substituted forelements thereof without departing from the scope of the disclosure. Inaddition, many modifications can be made to adapt a particular situationor material to the teachings of the disclosure without departing fromessential scope thereof. Therefore, it is intended that the disclosurenot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the disclosurewill include all embodiments falling within the scope of the appendedclaims.

The invention claimed is:
 1. A method for producing a highly purified2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I)

wherein R¹ is hydrogen or a C₁₋₃ alkyl group and R² is hydrogen, a C₁₋₃alkyl group, or a halogen, and wherein the method comprises: heating areaction mixture comprising a phenolphthalein compound of formula (II)

wherein R² is hydrogen, a C₁₋₃ alkyl group, or a halogen, a primary arylamine of formula (III),

wherein R¹ is hydrogen or a C₁₋₃ alkyl group, and an acid catalyst, toform a phthalimidine compound of formula (I); precipitating thephthalimidine compound from the reaction mixture to provide a crudephthalimidine compound; dissolving the crude phthalimidine compound inan aqueous solution comprising an alkali metal hydroxide, an alkalineearth hydroxide, or a combination comprising at least one of theforegoing metal hydroxides; precipitating the dissolved, crudephthalimidine compound from the aqueous base solution by adding amineral acid in an amount effective to lower the pH of the solution to9.0 to 12.0, to provide a semicrude phthalimidine compound; andisolating the semicrude phthalimidine compound from the aqueous basesolution, washing the isolated phthalimidine compound with dilute acid,then with water, and drying the washed phthalimidine compound to providea purified phthalimidine compound of formula (I); triturating thepurified phthalimidine compound of formula (I) with an aqueous C₁₋₃alcohol to provide a triturated phthalimidine compound; and washing thetriturated phthalimidine compound with aqueous alcohol, then hot waterpreheated to a temperature of 60 to 80° C.; and drying the washedphthalimidine compound to provide the highly purified2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine of formula (I), having aphenolphthalein compound content of less than 100 ppm, based on theweight of the 2-aryl-3,3-bis(4-hydroxyaryl)phthalimidine.